Gemini 3.5 Flash API: Control Thinking Levels in Python

Gemini 3.5 Flash API: Control Thinking Levels in Python

Google made Gemini 3.5 Flash generally available on May 19, 2026, and developers spent the week comparing it against the flagship models because the numbers looked strange in the best way: near-frontier reasoning at Flash speed. The interesting part for anyone writing code is not the leaderboard. It is that Google quietly changed how you control the model's reasoning. The old numeric thinking_budget you may have wired into a Gemini 2.5 project no longer applies. Gemini 3.5 Flash reasons through a four-step thinking_level enum instead, and the default effort dropped from high to medium.